Issue 28 – June 2011
Amendment 7 to B2/AS1, which comes into force in July 2011, applies only to Radiata pine and Douglas fir solid timbers that are within a closed space. Amendment 7 requires a minimum treatment of H1.2 boric. H1.2 boric treatment is also the minimum treatment required for floor joists, bearers, jack studs and solid flooring that is protected from the weather but exposed to ground atmosphere. Ceiling battens and 140 x 35 mm extra top plates are required to be constructed from H1.2 boric framing.
Other key requirements of Amendment 7 include:
- H3.2 treated timber is the minimum required for cantilevered enclosed deck joists and associated framing including joist trimmers, nogs, and blocking
- removal of LOSP treatments for H1.2 framing
- H3.1 treated timber remains the minimum allowable for cavity battens
- allowing buildings complying with all of the design parameters of Amendment 7 paragraph 18.104.22.168 to be constructed from untreated Douglas fir wall and roof framing.
To determine the durability requirements for other than solid Radiata pine and Douglas fir structural timbers and for appearance or non-framing timbers, designers and builders will need to continue to refer to NZS 3602:2003 Timber and wood-based products for use in buildings.
Information supplied by BRANZ.